Glossary

The terms in this glossary are defined as used in the VXIbus System. Although some of these terms may have different meanings in other systems, it is important to use these definitions in VXIbus applications. Terms which apply only to a particular instrument module are noted. Not all terms appear in every manual.

Accessed Indicator

An amber LED indicator that lights when the module identity is selected by the Resource Manager module, and flashes during any I/O operation for the module.

ACFAIL*

A VMEbus backplane line that is asserted under these conditions: 1) by the mainframe Power Supply when a power failure has occurred (either ac line source or power supply malfunction), or 2) by the front panel ON/ STANDBY switch when switched to STANDBY.

A-Size Card

A VXIbus instrument module that is 100.0 ⋅ 160 mm ⋅ 20.32 mm (3.9 ⋅ 6.3 in ⋅ 0.8 in), the same size as a VMEbus single-height short module.

Asynchronous Communication

Communications that occur outside the normal ªcommand-responseº cycle. Such communications have higher priority than synchronous communica- tion.

Backplane

The printed circuit board that is mounted in a VXIbus mainframe to provide the interface between VXIbus modules and between those modules and the external system.

B-Size Card

A VXIbus instrument module that is 233.4 ⋅ 160 mm ⋅ 20.32 mm (9.2 ⋅ 6.3 in ⋅ 0.8 in), the same size as a VMEbus double-height short module.

Bus Arbitration

In the VMEbus interface, a system for resolving contention for service among VMEbus Master devices on the VMEbus.

Bus Timer

A functional module that measures the duration of each data transfer on the Data Transfer Bus (DTB) and terminates the DTB cycle if the duration is excessive. Without the termination capability of this module, a Bus Master attempt to transfer data to or from a non-existent Slave location could result in an infinitely long wait for the Slave response.

VX1410A & VX1420A IntelliFrame Mainframe Instruction Manual

Glossary±1